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Updated: Dec 31, 2025
Determination of DNA Methylation of Imprinted Genes in Arabidopsis Endosperm
Published on: January 28, 2011
Involvement of MEM1 in DNA demethylation in Arabidopsis
Yanke Lu1, Jie Dai1, Liu Yang1
1College of Life Sciences, Nanjing Agricultural University, Nanjing, 210095, Jiangsu, China.
Key Message:
MEM1 participates in ROS1-mediated DNA demethylation pathway, and acts functionally as ROS3 to counteract the effects of RdDM pathway.mem1mutation leads to large numbers of hyper-DMRs inArabidopsisgenome. In higher plants, DNA methylation performs important functions in silencing transcribed genes and transposable elements (TEs). Active DNA demethylation mediated by REPRESSOR OF SILENCING 1 (ROS1) is able to antagonize the action of DNA methylation caused by RNA-directed DNA methylation (RdDM) pathway, which plays critical roles in keeping DNA methylation at a proper level. In this study, a new mutant named mem1 (for methylation elevated mutant 1) was isolated from a genetic screen of T-DNA insertional mutant population for lines with elevated DNA methylation at a particular locus through Chop-PCR method. MEM1 possesses a Zf-C3HC domain, and is localized in nucleus as well as highly expressed in cotyledons. Whole-genome bisulfite sequencing data showed that knockout mutation of MEM1 leads to 4519 CG, 1793 CHG and 12739 CHH hyper-DMRs (for differentially methylated regions). Further analysis indicated that there are 2751, 2216 and 2042 overlapped CG hyper-DMRs between mem1-1and three mutants, i.e. ros1-4, rdd and ros3-2, respectively; 797, 2514, and 6766 overlapped CHH hyper-DMRs were observed between mem1-1 and three such mutants, respectively; mem1 nrpd1-3 and mem1 rdm1 double mutants showed nearly complete or partial loss of hypermethylation at 4 tested loci, suggesting that MEM1 performs similar functions as DNA glycosylase/lyases in counteracting excessive DNA methylation, and MEM1 plays important roles as REPRESSOR OF SILENCING 3 (ROS3) in erasing CHH methylation caused by the RdDM pathway. Together, these data demonstrate the involvement of MEM1 in ROS1-mediated DNA demethylation pathway and functional connections between MEM1 and ROS3.
Insights
A new gene, MEM1, is identified to counteract DNA methylation in Arabidopsis. Mutations in MEM1 cause widespread DNA hypermethylation, highlighting its role in the ROS1-mediated demethylation pathway.
Area of Science:
- Plant Molecular Biology
- Epigenetics
- Genomics
Background:
- DNA methylation is crucial for gene silencing and transposon control in plants.
- The RNA-directed DNA methylation (RdDM) pathway establishes DNA methylation, while active demethylation pathways, like ROS1, counteract it.
- Maintaining proper DNA methylation levels is essential for genome stability and gene regulation.
Purpose of the Study:
- To identify novel components involved in DNA methylation regulation in Arabidopsis.
- To elucidate the function of the MEM1 gene in the context of DNA methylation and demethylation pathways.
- To understand the relationship between MEM1, ROS1, and the RdDM pathway.
Main Methods:
- Genetic screening of T-DNA insertion mutants to identify lines with altered DNA methylation.
- Chop-PCR for initial screening of methylation levels.
- Whole-genome bisulfite sequencing (WGBS) for comprehensive methylation analysis.
- Analysis of double mutants to assess functional redundancy and interactions.
Main Results:
- The mem1 mutant exhibits a significant increase in DNA methylation across the genome, with numerous hyper-differentially methylated regions (hyper-DMRs) in CG, CHG, and CHH contexts.
- MEM1 shows functional overlap with ROS3 and plays a role in counteracting RdDM-mediated methylation, particularly affecting CHH methylation.
- MEM1 is involved in the ROS1-mediated DNA demethylation pathway, indicating its importance in balancing methylation levels.
Conclusions:
- MEM1 is a key player in the active DNA demethylation pathway, functioning alongside ROS1 and ROS3.
- MEM1 acts to suppress excessive DNA methylation, particularly that established by the RdDM pathway.
- The discovery of MEM1 provides new insights into the complex epigenetic regulatory network controlling DNA methylation in plants.
